CVE-2023-33010

A buffer overflow vulnerability in the ID processing function in Zyxel ATP series firmware versions 4.32 through 5.36 Patch 1, USG FLEX series firmware versions 4.50 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.25 through 5.36 Patch 1, USG20(W)-VPN firmware versions 4.25 through 5.36 Patch 1, VPN series firmware versions 4.30 through 5.36 Patch 1, ZyWALL/USG series firmware versions 4.25 through 4.73 Patch 1, could allow an unauthenticated attacker to cause denial-of-service (DoS) conditions and even a remote code execution on an affected device.

CVSS: 9.8Criticalscored by the publisher (CNA)
Exploited in the wild: Yes, in CISA KEV since 5 Jun 2023CISA deadline for US federal agencies: 26 Jun 2023
EPSS: 29.0%chance of exploitation in the next 30 daystop 2% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 24 May 2023analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Attack surface: Server-side
Exploitable: At runtime
Attack vector: network
Weakness: CWE-120 Buffer Overflow
Can a WAF block it?: No. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Product	Affected versions	Vendor says fixed in
Zyxel ATP series firmware	4.32 through 5.36 Patch 1Vendor says fixed in: not stated	Not stated by the vendor
Zyxel USG20(W)-VPN firmware	4.25 through 5.36 Patch 1Vendor says fixed in: not stated	Not stated by the vendor
Zyxel USG FLEX 50(W) firmware	4.25 through 5.36 Patch 1Vendor says fixed in: not stated	Not stated by the vendor
Zyxel USG FLEX series firmware	4.50 through 5.36 Patch 1Vendor says fixed in: not stated	Not stated by the vendor
Zyxel VPN series firmware	4.30 through 5.36 Patch 1Vendor says fixed in: not stated	Not stated by the vendor
Zyxel ZyWALL/USG series firmware	4.25 through 4.73 Patch 1Vendor says fixed in: not stated	Not stated by the vendor

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

Products named in our analysis

zyxel:atp100_firmware
zyxel:atp200_firmware
zyxel:atp500_firmware
zyxel:atp100w_firmware
zyxel:atp700_firmware
zyxel:atp800_firmware
zyxel:usg_flex_100_firmware
zyxel:usg_flex_50_firmware
zyxel:usg_flex_200_firmware
zyxel:usg_flex_500_firmware
zyxel:usg_flex_700_firmware
zyxel:usg_flex_100w_firmware
zyxel:usg_flex_50w_firmware
zyxel:usg_20w-vpn_firmware
zyxel:vpn100_firmware
zyxel:vpn50_firmware
zyxel:vpn300_firmware
zyxel:vpn1000_firmware
zyxel:usg20-vpn_firmware
zyxel:usg_40_firmware
zyxel:usg_40w_firmware
zyxel:usg_60w_firmware
zyxel:usg_60_firmware

Fix and mitigation

WAF and other mitigations

Can a WAF block it? No. This is a buffer overflow. Generic WAF rules do not recognise the input that triggers it; only a rule written for this specific CVE can, and only if the triggering request has a recognisable shape.

Also consider: patch

Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 5 Jun 2023.
CISA due date: 26 Jun 2023, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
CISA SSVC: exploitation active, automatable yes, technical impact totalAssessed by CISA 16 Jan 2025 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Timeline

24 May 2023Published
5 Jun 2023Added to CISA KEV (exploited in the wild)11 days later
26 Jun 2023CISA remediation due date (US federal agencies)21 days later
16 Jan 2025CISA SSVC assessment: exploitation active571 days (about 2 years) later
21 Oct 2025CVE record last updated278 days (about 9 months) later
12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Metric	Value	What it means
Attack vector	NetworkReachable over the internet or any routable network.	Reachable over the internet or any routable network.
Attack complexity	LowRepeatable attack, no special conditions.	Repeatable attack, no special conditions.
Privileges required	NoneThe attacker needs no prior access.	The attacker needs no prior access.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	HighComplete modification possible.	Complete modification possible.
Availability	HighFull outage possible.	Full outage possible.

Common questions

Is CVE-2023-33010 being exploited?

Yes. CVE-2023-33010 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2023-33010?

CVE-2023-33010 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2023-33010?

Yes. A fix has been recorded for CVE-2023-33010. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2023-33010 affect?

CVE-2023-33010 affects zyxel:atp100_firmware, zyxel:atp200_firmware, zyxel:atp500_firmware, zyxel:atp100w_firmware, and 19 further products or versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

2 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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